A process for synthesizing concentrated bleach is described in patent application EP 0 527 083. The synthesis is carried out by reacting one molecule of chlorine with sodium hydroxide. Due to its concentration, this “high titer” bleach is particularly economically advantageous since it makes it possible to limit transport costs. Indeed, since the amount of water in a high-titer bleach is lower than in a standard bleach, less water is transported for the same amount of bleach. Moreover, the high-titer bleach obtained by the above process contains little salt after dilution, which provides great stability over time.
Nevertheless, the synthesis of high-concentration bleach results in parasitic reactions being favored, such as the reaction resulting in the formation of chlorate according to the following reaction:3NaClO→□NaClO3+2NaCl
This reaction generally results in the formation of chlorate during the synthesis, in a greater amount in high-titer bleach compared to bleaches obtained by other processes.
However, the presence of chlorate in the bleach constitutes a major drawback when this bleach has, for example, to be added to drinking water. Indeed, when bleach is added to drinking water, the regulations usually require a very low content of chlorate.